This invention relates to a closure or lid for a vacuum food container and of the type disclosed in applicant's U.S. Pat. Nos. 5,979,688 and 6,206,220, the entire disclosure of which is incorporated by reference. These patents are directed to a thin sheet metal closure or cap or lid for a vacuum packed and sealed food container wherein the closure is removably sealed to the container and reclosable on the container. Commonly, the container is formed of glass but may also be formed plastic or sheet metal, and the vacuum within the sealed container is released to facilitate or simplify the removal of the closure or lid from the container with reduced torque. Other forms of containers with reusable closures for vacuum food containers and having a vacuum release structure before the closure is removed from the container are disclosed in U.S. Pat. No. 3,410,436 and U.S. Patent Publication No. US 2014/0103044.
As used herein, the term container includes a glass or sheet metal or plastic container, and the term lid includes any form of closure such as a twist-on, twist-off sheet metal cap or a press-on, press-off sheet metal cap or lid for a container. The lid has a peripheral chime or rim portion with a bonded sealant material to form a releasable sealed coupling between the lid and the container. In such an enclosed vacuum food container and lid assembly, it has been found desirable to add an easily activated vacuum release button to the lid after the lid has been completely formed on tooling which shapes the lid and has the bonded sealant material on the inner surface of the rim portion of the lid. It would be desirable to minimize the thickness of the sheet metal, such as sheet steel or aluminum, which forms the lid and to provide a clearly visible tamper-proof indication when the vacuum has been released from the container.